During the past decade, many studies in developmental biology have focused on the signal transduction that initiates developmental events. This approach has been extremely productive and has led to the identification of highly conserved signaling pathways. For example, members of the Wnt and Ras pathways have been well-characterized using developmental genetics and also play critical roles in human disease, most visibly cancer. A current challenge in developmental biology is to build upon our knowledge of "backbone" signaling pathways like Wnt and Ras and describe more fully the events occurring downstream of these pathways. We propose to use vulval development in C. elegans as a model system to study the events downstream of the RTK/Ras/MAP kinase cascade. Initially, we will focus on the genetic and molecular characterization of two previously identified genetic loci that act downstream of Ras in vulval development. Since little is known about factors or targets downstream of the Ras pathway, characterization of these genes will likely provide new knowledge about the downstream control of this conserved signaling pathway. In addition, we propose a screen to identify new genes involved in the events far downstream of the events initiated by Ras. Specifically, we plan to identify genes involved in the execution of vulval morphogenesis.